In known spark erosion machines, the electrode is moved towards the workpiece to be machined at a constant speed until the desired working gap of a few hundredths of a millimeter is reached, and the electrode is then stopped in order to be advanced at normal machining speed. This rapid approach movement of the electrode causes an extremely high pressure to be built up in the dielectric in the region of the working gap, because the dielectric can only slowly escape because of the small distance between the electrode and the workpiece. The pressure in the dielectric produces a force which opposes the approach movement of the electrode towards the workpiece. In many cases, this force is so high that the electrode or the electrode carrier are damaged.
The constant approach speed of the electrode to the workpiece also results in the electrode running into the workpiece and thus causing a short-circuit which can only be stopped by subsequently retracting the electrode.
An object of the invention is to avoid the disadvantages of the known art, and in particular therefore to provide a process and apparatus in the use of which no pressure peaks are produced in the dielectric and at the same time the forces required for moving the electrode to the workpiece can be reduced to a minimum.
Another object of the invention is to control the approach movement of the electrode towards the workpiece in such a way that no short-circuit can occur during this operation.
The invention also provides apparatus for carrying out the process.